This disclosure concerns adjustable seats, such as seats in industrial, construction, farming and commercial vehicles, and particularly to seats capable of adjustments of height and tilt of the seat.
Seats are a critical component for the comfort of a driver, particularly for drivers of heavy duty vehicles, such as farm tractors, construction vehicles, and the like. Drivers of vehicles of these types are often seated for long periods of time so the driver's comfort level will often change throughout the day. Moreover, the drivers themselves may change from day-to-day or job-to-job, with each driver having his/her own comfort preferences.
One key comfort component for vehicle seats is the seat height and the angle of tilt of the seat relative to the dashboards or controls of the vehicle. Consequently, many seat assemblies include one or more mechanisms for adjusting the height and angle of the seat. In some vehicles, the two adjustments are made by two independent mechanisms. In more sophisticated seats assemblies, the height and angle adjustments are combined into a common mechanism. One such system is depicted in FIGS. 1-8. The seat assembly 10 includes a seat 12 having a conventional seat back 12a and seat bottom 12b, with the seat bottom supported on a base 13 that is mounted to the vehicle. The base may be configured to allow linear front-back movement of the seat assembly, and may even permit rotation of the seat assembly or seat bottom to facilitate access to the seat.
The seat assembly 10 includes an adjustment assembly 15 that includes upper frame members 16 configured to be mounted to the seat bottom 12b in a conventional manner. As best shown in FIGS. 3-5, the adjustment assembly 15 includes front and rear pivot bars 18f, 18r mounted between the upper frame members 16. A corresponding front and rear lever arm 19f, 19r is mounted to the respective pivot bar 18f, 18r so that the lever arm can pivot about a horizontal axis. The lever arms 19f, 19r may be pivotably mounted on the pivot bar 18f, 18r, or the pivot bar may be mounted for rotation relative to the frame with the lever arms fixed to the respective pivot bars.
A pivot post 21f, 21r projects horizontally from the free end of the corresponding lever arm 19f, 19r. A pivot arm 20f, 20r is pivotably mounted to a respective lever arm 19f, 19r by a corresponding pivot post 21f, 21r so that the lever arm can pivot relative to the pivot arm, even as the pivot arm can pivot relative to the frame. A torsion spring 22 is mounted on each pivot post 21f, 21r to apply a torsional spring force to the pivot atm 20f, 20r. Each pivot arm defines a base mount 23f, 23r that is configured to be engaged to the seat base 13 in a conventional manner. It can be appreciated that when the base mounts 23f, 23r are fastened to the seat base, the torsion springs 22 generate a torsional spring force that tends to pivot the respective pivot arms 20f, 20r away from the base. By virtue of the interface between the pivot arms and the frame 16, as discussed below, this pivoting of the pivot arms away from the seat base manifests in an upward movement of the seat bottom 12b mounted to the frame. This upward movement adjusts the height of the seat assembly and a differential upward movement of the front or back adjustment assemblies 15f, 15r produce the seat tilt.
In this prior adjustment assembly 15, a sliding bar 25f, 25r is engaged between the pivot arms 20f, 20r arranged at opposite sides of the frame 16. The sliding bars thus ensure that the front pivot arms 20f at opposite sides of the assembly 15 move in unison, and that the rear pivot arms 20r at opposites of the assembly 15 also move in unison. The sliding bars 25f, 25r are sized to extend horizontally and laterally through slots 26f, 26r defined in the opposite sides of the frame 16. In the specific assembly shown in FIGS. 1-8, latches 28f, 28r are mounted to the ends of the respective sliding bars 25f, 25r and are configured to slidably support the ends of the bars within the corresponding slots 26f, 26r. The latches are configured to permit smooth and uniform sliding of the sliding bars relative to the frame 16.
It can be appreciated that the lever arms 19f, 19r, the pivot arms 20f, 20r, and the sliding bars 25f, 25r engaged within the slots 26f, 26r, form a three-bar linkage so that rotation of the pivot arm 20f, 20r under operation of the torsion spring 22 causes the sliding bars 25f, 25r and pivot bars 18f, 18r to move upward as the sliding bars slide along the slots 26f, 26r, and causes the angle subtended by the lever arm and pivot arm to decrease. The three-bar linkages of the adjustment assemblies 15f, 15r are configured so that the frame 16, and therefore the seat bottom 12b, is parallel to the base 13 when the lever arms are all at their maximum and minimum ranges of motion.
The adjustment assemblies 15f, 15r include a mechanism to limit the movement of the lever arms and thus the height of the front and the rear of the seat. One latch 28f, 28r mounted to the respective sliding bar 25f, 25r is engaged by a corresponding engagement latch 30f, 30r, as shown in the detail views of FIG. 5. Each latch 28f, 28r defines a notch 34, and each engagement latch 30f, 30r defines a plurality of notches 35 that are sized to engage the notch 34 of the latches 28f, 28r. When the notches 34, 35 are engaged to each other the sliding bar 25f, 25r is prevented from sliding along the slot 26f, 26r, thereby fixing the position of the sliding bar and consequently the orientation of the three-bar linkage of the adjustment assembly 15f, 15r. The notches 35 in the engagement latches 30f, 30r are spaced along the length of the slots 26f, 26r to define the range of motion of the sliding bars and thus the range of vertical movement of the frame 16 and seat bottom 12b relative to the base 13. The engagement latches are mounted to a respective rotation rod 31f, 31r that can be rotated by a respective handle 32f, 32r. Rotation of the handle, and thus the rotation rod 31f, 31r, moves the notches 35 of the engagement latch 30f, 30r into and out of engagement with the notch 34 of the latch 28. When the notches are out of engagement the vehicle driver can physically adjust the height of the front and back of the seat, depending upon which lever 32f, 32r is operated. The torsion springs 22 inherently bias the front and back of the seat upward so that the driver can use his/her weight to control how far upward the front and/or back of the seat is moved. Once the seat has been adjusted to the driver's preference the respective handle 32f, 32r can be rotated to engage the notches 34, 35 of the latch 28f, 28r and engagement latch 30f, 30r. 
As demonstrated in FIGS. 6-8, the driver can adjust the height and angle of the seat by manipulating the two handles 32f, 32r. The height can be adjusted by moving both adjustment assemblies 15f, 15r in the same manner. The angle can be adjusted for a forward tilt by moving the rear adjustment assembly 15r more than the front assembly 15f, as shown in FIG. 7a, and for a rearward tilt by adjusting the front adjustment assembly 15f, as depicted in FIG. 7b. Adjusting both assemblies 15f, 15r by the same amount can adjust the height of the seat, as shown in FIGS. 7c, 7d. The chart and graph in FIG. 8 illustrate the range of angles and heights based on the position of the front and rear adjustment assemblies.